1. Field of the Invention
The present invention relates to a multilayered circuit board suitable for use in an electric circuit of a band-pass filter or the like.
2. Description of the Related Art
Known multilayered circuit boards will be described. FIG. 8 is an exploded perspective view of a known multilayered circuit board in which an inductor and a capacitor are connected in parallel; FIG. 9 is a circuit diagram of the multilayered circuit board of FIG. 8; FIG. 10 is an exploded perspective view of a known multilayered circuit board in which an inductor and a capacitor are connected in series; and FIG. 11 is a circuit diagram of the multilayered circuit board of FIG. 10.
Referring to FIG. 8, the arrangement of the multilayered circuit board in which an inductor and a capacitor are connected in parallel will be described. First, second, and third ceramic insulating layers 51, 52, and 53 are stacked on top of each other in layers.
The first insulating layer 51 has a first rectangular electrode 54 formed of a conductive film of silver or the like on the surface. The first electrode 54 has a first extension 55.
The second insulating layer 52 has a first U-shaped electric conductor 56 formed of a conductive film of silver or the like on the surface. The first electric conductor 56 has a hole 56a at a first end and the first electrode 54 has a hole 54a, which have a connector such as a through hole (not shown) to electrically connect the first end of the first electric conductor 56 and the first electrode 54.
The third insulating layer 53 has a second rectangular electrode 57 formed of a conductive film of silver or the like on the surface. The second electrode 57 has a second extension 58.
The first electric conductor 56 has a hole 56b at a second end and the second electrode 57 has a hole 57a, which have a connector such as a through hole (not shown) to electrically connect the second end of the first electric conductor 56 and the second electrode 57.
The multilayered circuit board with such an arrangement has a capacitor C formed of the first and second electrodes 54 and 57 opposed to each other through the first and second insulating layers 51 and 52, and an inductor L formed of the first electric conductor 56.
Accordingly, as FIG. 9 shows, the inductor L and the capacitor C are connected in parallel between the first and second extensions 55 and 58.
Referring now to FIG. 10, the arrangement of the multilayered circuit board in which an inductor and a capacitor are connected in series will be described. First, second, and third ceramic insulating layers 61, 62, and 63 are stacked on top of each other in layers.
The first insulating layer 61 has a first U-shaped electric conductor 64 formed of a conductive film of silver or the like on the surface. The first electric conductor 64 has a first extension 65 at a first end.
The second insulating layer 62 has a first rectangular electrode 66 formed of a conductive film of silver or the like on the surface. The first electrode 66 has a hole 66a and the first electric conductor 64 has a hole 64a at a second end, which have a connector such as a through hole (not shown) to electrically connect the second end of the first electric conductor 64 and the first electrode 66.
The third insulating layer 63 has a second rectangular electrode 67 formed of a conductive film of silver or the like on the surface. The second electrode 67 has a second extension 68.
The multilayered circuit board with such an arrangement has a capacitor C formed of the first and second electrodes 66 and 67 opposed to each other through the second insulating layer 62 and an inductor L formed of the first electric conductor 64.
Accordingly, as FIG. 11 shows, the inductor L and the capacitor C are connected in series between the first and second extensions 65 and 68.
The known multilayered circuit boards including the inductor and the capacitor require at least three insulating layers, thus disadvantageously including a large number of components to increase the cost and the thickness.
The use of three insulating layers poses the problems of requiring much time and labor for production and needing through-hole conduction work in at least one part, thus decreasing production efficiency.